This invention relates to the fabrication of a plastic article. More particularly, this invention relates to a method and system for laser welding a plastic manifold.
Plastic manifolds have become increasingly utilized in automotive applications because they provide advantages including the reduction of weight, and cost as compared to manifolds fabricated utilizing metal alloys. Further, plastic intake manifolds allow the formation of shapes that are otherwise difficult, and cost prohibitive with the casting methods required for utilizing metal alloys.
The fabrication of a plastic manifold includes the joining of several different parts into a completed manifold. Joining of the different parts is often performed by ultrasonic, or vibration welding. Ultrasonic and vibration welding require relatively complex joint configurations between each of the different parts. Further, due to the complex joint configuration, a complete intake manifold may require many parts that are joined in several different joining operations. As appreciated, each operation contributes detrimentally to the potential for defects and overall cost.
An improved method of joining plastic manifold parts includes the use of a laser beam for welding the desired parts together. A laser welding process utilizes a laser beam to melt plastic in a localized region between the two parts to be joined. Typically, only a simple lap joint is required between parts. The laser welding process utilizes a laser transparent material through which the laser beam is directed. A laser absorbent material is disposed against the laser transparent part on a side opposite the laser beam. Laser energy is transmitted through the laser transparent part and absorbed by the laser absorbent part. The absorbed laser energy heats and melts the two parts in the localized area between the two pieces. The molten plastic is then allowed to cool forming the desired joint.
Laser welding requires a minim gap between the two parts to be welded, or the laser energy and heat from the laser does not sufficiently heat the two parts that are to be joined. Further, the laser beam must be aligned with the joint in such a way as to align the focal point of the laser beam such that it heats the two parts. Any discontinuities or surface features that interfere with the path of the laser beam can disrupt the focal point of the laser beam. Additionally, because laser energy is focused to provide the desired energy at a point within the material, the thickness of the part is typically preferred to be substantial uniform. The uniformity of the parts provides the penetration of the laser energy that in turn provides the desired joint.
Disadvantageously, the requirements on part design to facilitate laser welding can limit the desired appearance and design of a plastic part. Further, in some instances, variations in part thickness are desired to provide specific desired performance features. Additionally, some applications are not attempted with laser welding due to desired surface features that complicate the laser welding process.
Accordingly, it is desirable to design a method and system for applying laser welding processes to plastic articles having differing exterior configurations.